Many electronic devices require application of an adhesive or insulation materials, such as glue, solder or epoxy, as part of the device structure. It is desirable for the application of such materials to fall within tight tolerances for proper reliability and minimized materials use to reduce costs.
Solder paste inspection (SPI) devices are currently available that measure the height of solder applied to a printed circuit board. Conventional SPI devices use structured light directed vertically onto the solder to be measured. As is well known in the art, solder is a non-transparent, colored material. Diffuse reflected light is collected and measured to determine a height of the solder. However, the SPI device is only effective for measuring the height of a non-transparent, colored solder. Conventional SPI devices are not able to measure the height of a transparent material, such as transparent glue.
To measure the height of a transparent material, a manual process is performed whereby an operator places the object including the transparent material to be inspected under a microscope. A series of operations are manually performed using various settings on the microscope, and a height is determined using obtained measurements. This a time consuming process and the results may have large variances.